SEMICONDUCTOR DEVICE

Abstract: A semiconductor chip (3) is disposed in a device hole (23) of a circuit substrate (2) equipped with an insulating flexible substrate material (21). Bumps (31) of the semiconductor chip (3) are connected by single-point bonding to leads (221) protruding inside the device hole (23) from a conductor pattern (22). The circuit substrate (2) includes superposition portions (211) of the substrate material (21) superposing with the semiconductor chip (3) at four corner portions of the device hole (23), and superposition portions (212) that divide each device hole (23) into four holes (231 to 238). A dummy bump (32), which is interposed between the circuit substrate (2) and the semiconductor chip (3) and secures a predetermined gap between them, is disposed on the face of the semiconductor chip (2) superposing with these superposition portions (211, 212), without being coupled to the conductor pattern (22). A through-hole (230) for escaping air when a mold material is injected from the holes (231 to 238) is formed in the superposition portion (212).

Description: Field of technology This invention relates to a semiconductor device, particularly one equipped with a structure suitable for the assembly of a relatively large-sized semiconductor chip, and a structure suitable for the assembly of a semiconductor chip onto a flexible circuit board that is often used in quartz watch applications. Background technology In the assembly of a semiconductor chip onto a circuit board, such as shown in Figure 7, a molding agent [55] is injected through a device hole [53], after the lead [521] of the conductive pattern [52] formed on the circuit board [51], which protrudes into the device hole [53], is bonded to the bump [541] of the semiconductor chip [54]. This lead [521] is usually formed downward to prevent short-circuiting between the edge of the semiconductor chip [54] and the conductive pattern [52]. However, in this type of assembly structure, the lead [521] is bent to a great degree, with the result of increasing the thickness of the semiconductor device. Furthermore, during the lead-forming process, increases in the number of leads [521] also result in increases in the irregularity of the shape and position of each lead. Consequently, in the assembly of a large-sized semiconductor chip [54], these forming-related irregularities result in some of the bumps [541] not being bonded to the leads [521]. Furthermore, the device hole [55] must be enlarged as the size of the semiconductor chip [54] increases, thus increasing the planar area of the semiconductor device. For this reason, this assembly method cannot be used in electronic instruments, such as quartz watches, which require small size. One possible method of increasing stability against warpage, etc., in the assembly of a large-size semiconductor chip [54], is as follows. Reinforcing dummy bumps, which are electrically insulated from the internal circuit, are formed on the side of the semiconductor chip [54]. Bonding in the additional areas made available by these dummy bumps is used to increase the bonding strength between the semiconductor chip [54] and the circuit board [52]. However, the dummy bump connection used in this type of structure also requires a forming process, and thus the above-mentioned problems associated with the forming process cannot be eliminated. Another assembly structure suitable for achieving thin semiconductor device profile uses a method in which a solder bump [62] formed on the semiconductor chip [61] is heated under pressure and bonded with the conductive pattern [64] of the circuit board [63], as shown in figure 8. In this type of assembly structure, because part of the circuit board [63] overlaps the active area of the semiconductor chip [61], the conductive pattern [64] can also be formed in this overlapping area. This results in a high degree of pattern design freedom, which is suitable to achieving thin semiconductor device profile. However, the solder bump [62] does require a complicated manufacturing process, thus resulting in high manufacturing cost. Furthermore, because the semiconductor chip [61] must be heated first and then cooled during the process of assembling the semiconductor chip [61] onto the circuit board [63], the resulting long manufacturing throughput makes it difficult to reduce costs. In assembly structure using this kind of solder bump [62], possible methods of preventing short-circuiting between the circuit board [63] and the semiconductor chip [61] include increasing the thickness of the solder bump [62], or forming dummy solder bumps. However, as long as solder bumps are used, the above-mentioned manufacturing-related problem will remain. Another method of bonding a semiconductor chip to a circuit board is described in Japanese Patent Publication No. 03-126237, in which a semiconductor chip is secured by solder bumps to leads of a conductive pattern on a circuit board and insulating spacers are provided on the leads adjacent the contact regions to ensure that the leads do not come into contact with the edge of the semiconductor chip. Yet another method of securing a semiconductor chip to a circuit board is shown in Japanese Patent Publication No. 62-086737 in which a semiconductor chip is bonded to electrodes of a conductive pattern on the surface of an insulating substrate and holes are formed in the substrate between the leads of the conductive pattern to allow a molding agent to be injected into the space between the substrate and the semiconductor chip to secure the semiconductor chip in place. A yet further method of securing a semiconductor chip to a substrate is shown in Japanese Patent Publication No. 63-95639 which describes a substrate bearing a conductive lead pattern for connection to a semiconductor chip in which the lead portions of the conductive pattern which are bonded the semiconductor chip project over holes in the substrate. The holes in the substrate are separated by a superimposing area overlapping the semiconductor chip to securely mount the semiconductor chip to the substrate. A yet further method of securing a semiconductor chip to a substrate is shown in Japanese Patent Publication No. 53-123074 in which a semiconductor chip is compression bonded to leads supported by a substrate and in addition to bonding projections provided on the semiconductor chip additional spacer projections are provided to ensure that the leads cannot contact the edges of the semiconductor chip. In order to solve these problems, the invention is intended to provide thinner-profile, lower-cost semiconductor devices, while achieving reliability superior to that attainable using conventional assembly structures, even when single-point or gang bonding methods are used. Additionally, the invention is intended to provide semiconductor devices with improved pattern design freedom. Disclosure of the invention In a first aspect, this invention provides a semiconductor device comprising: a circuit board in which a conductive pattern has been formed on an insulating substrate, a semiconductor chip positioned over a device hole of the said circuit board and a plurality of spacers; wherein a lead portion of the conductive pattern protruding into the said device hole is bonded to a bonding electrode of the said semiconductor chip and the said circuit board possesses a superimposing area overlapping the said semiconductor chip, the superimposing area being formed by superimposing one upon the other a part of said insulating substrate and the conductive pattern, the conductive pattern being arranged on the said part of said insulating substrate such that it faces toward the semiconductor chip, and characterised in that the said plurality of spacers is provided on a surface of the said superimposing area and not bonded with the said semiconductor chip and/or is provided on a surface of the area of the said semiconductor chip overlapping said superimposing area and not bonded with the said superimposing area, at least one portion of the conductive pattern being arranged on a region of the substrate existing between a spacer and an adjacent spacer, such that the said spacers are positioned outside the device hole between the said circuit board and the said semiconductor chip to maintain a specified gap between the two. In a second aspect, this invention provides a method of producing a semiconductor device comprising: a circuit board in which a conductive pattern has been formed on an insulating substrate, and a semiconductor chip is positioned over a device hole of the said circuit board and the said circuit board possesses a superimposing area overlapping the said semiconductor chip, the superimposing area being formed by superimposing one upon the other a part of said insulating substrate and the conductive pattern, the conductive pattern being arranged on the said part of said insulating substrate such that it faces toward the semiconductor chip; characterised by: forming a plurality of spacers on a surface of the said superimposing area and/or on a surface of the area of the said semiconductor chip overlapping said superimposing area, at least one portion of the conductive pattern being arranged on a region of the substrate existing between a spacer and an adjacent spacer, positioning the semiconductor chip over the device hole and bonding a lead portion of the conductive pattern protruding into the said device hole to a bonding electrode of the said semiconductor chip the spacers formed on the surface of the superimposing area being not bonded with the semiconductor chip and/or to bring the spacers formed on the surface of the semiconductor chip being not bonded with the superimposing area, such that the said spacers are positioned outside the device hole between the said circuit board and the said semiconductor chip to maintain a specified gap between the two. For example, the invention is characterised in that dummy bumps are formed on the part of the semiconductor chip that overlaps the superimposing area, such that the said dummy bumps are not bonded to the conductive pattern, and which act as the spacer that maintains a specified distance between the circuit board and the semiconductor chip. In other words, a specified distance is automatically maintained between the circuit board and the semiconductor chip by the dummy bumps, which are not flattened during the bonding process, and thus retain the same thickness. This prevents the occurrence of short-circuiting between the edge of the semiconductor chip and the conductive pattern. Therefore, a forming process need not be applied to the leads when either single-point or gang bonding methods are used. Furthermore, it removes the necessity for solder bumps, reducing the cost of which is difficult. Because of these factors, it is possible to produce a semiconductor device possessing higher reliability, thinner profile, and lower cost than conventional semiconductor devices. High reliability is obtained because the gap dimension is determined by the pre-established initial thickness of the spacer, e.g., dummy bumps. Additionally, dummy bumps do not raise semiconductor chip cost since they can be formed simultaneously with the bumps for bonding. In this invention, "dummy" means that no electrical circuit connection is required, and the above-mentioned dummy bumps, as well as the dummy pads mentioned later, are electrically insulated from the internal circuit of the semiconductor chip. Furthermore, in this invention, a "bump" refers to a thick electrode that protrudes from areas such as the active area of the semiconductor chip, and a "pad" to an electrode that does not protrude from the active area of the semiconductor chip. In addition to dummy bumps and dummy pads, it is possible to use as spacers, dummy conductive patterns which are not electrically connected to other electrical circuits on the circuit board side, and for which no electrical circuit connection is required. In this invention, it is desirable that the conductive pattern overlap the dummy bumps in the superimposing area. This is because the gap between the edge of the semiconductor chip and the conductive pattern can be better maintained when the dummy bumps overlap the conductive pattern itself. Another example of the invention is characterized in that a protruding conductive pattern is formed, which is not bonded to the bonding electrode, and which acts as a spacer that maintains a specified distance between the circuit board and the semiconductor chip. In this case also, a specified distance is automatically maintained between the circuit board and the semiconductor chip by the protruding conductive pattern, which is not flattened by the bonding process, thus retaining its initial thickness. For this reason, no forming process is required when either single-point or gang bonding methods are used. In this case, it is more desirable for bumps to be formed on the semiconductor chip side as bonding electrodes, and for dummy bumps, which are not to be bonded to the protrusions, to be formed in those locations corresponding to the protrusions. This is because the gap dimension can be expanded in proportion to the thickness of the dummy bump. It is also acceptable for pads to be formed on the semiconductor chip side as bonding electrodes, and for dummy pads, which are not to be bonded to the protrusions, to be formed in those locations corresponding to the protrusions. In this invention, in those cases in which the device holes are approximately quadrangular in outline, it is better if superimposing areas are formed in the four corner areas. Furthermore, it is desirable that superimposing areas also be formed on each side of the device holes. This allows a stable distance to be maintained between the circuit board and the semiconductor chip. Furthermore, it is desirable that a superimposing area be formed inside the device hole, dividing the said device hole into multiple holes. This allows the molding agent to spread more easily when injected through multiple holes. In particular, it is desirable that the superimposing area cross the approximate center of the device hole, dividing it into multiple holes, and that a through-hole be formed in the section of the superimposing area corresponding to the approximate center of the device hole. This through-hole is intended to facilitate the escaping of air when a molding agent is injected. Furthermore, if the device hole is divided into multiple holes, a conductive pattern possessing an area that crosses over the hole can be formed when positioning the wiring on the active side of the semiconductor chip. This type of cross-over area is very strong because it is supported and reinforced by the superimposing area. Therefore, it becomes possible to increase the design freedom of the wiring pattern. Brief explanation of figures Figure 1 is a top view of the configuration of the semiconductor device related to Working example 1 of the invention. Figure 2 (a) shows a longitudinal section of Figure 1, along Line I - II; while Figure 2 (b) shows a longitudinal section of Figure 1, along Line I - III. Figure 3 (a) is a longitudinal section that schematically shows the structure of the semiconductor device related to working example 1 of the invention before bonding, while Figure 3 (b) is a longitudinal section that schematically shows the structure of the semiconductor device in Working example 1 of the invention after bonding. Figure 4 (a) is a longitudinal section that schematically shows the structure of the semiconductor device related to Working example 2 of the invention before bonding, while Figure 4 (b) is a longitudinal section that schematically shows the structure of the semiconductor device in Working example 2 of the invention after bonding. Figure 5 (a) is a longitudinal section that schematically shows the structure of the semiconductor device related to Working example 3 of the invention before bonding, while Figure 5 (b) is a longitudinal section that schematically shows the structure of the semiconductor device in Working example 3 of the invention after bonding. Figure 6 shows another working example of the invention, and is a cross section that schematically shows the bonding process using the gang-bonding method used for the semiconductor device related to Working example 1. Figure 7 is a longitudinal section showing the configuration of a conventional semiconductor device. Figure 8 is a longitudinal section showing the configuration of another conventional semiconductor device. The ideal mode for implementation of the invention The semiconductor devices related to the invention are explained below, with references to the various figures. Working example 1 Figure 1 shows the top view of the semiconductor device related to Working example 1 of the invention. Figure 2 (a) shows a longitudinal section of Figure 1, along Line I - II; and Figure 2 (b), a longitudinal section of Figure 1, along Line I - III. In Figures 1, 2 (a), and 2 (b) , the semiconductor device [1] in the example is used as a circuit block in an analog multi-function electronic watch, and consists of a circuit board [2] and a semiconductor chip [3] containing a CPU. The active area [30] of the semiconductor chip [3] is approximately 5 mm x 5 mm in size, on which 36 bumps [31] that require bonding have been formed. Semiconductor chips ordinarily used for quartz watches are approximately 2 mm x 2 mm in size, and possess over 10 bumps. Thus, the semiconductor chip [3] in this example possesses approximately six times the area of and more than twice the number of bonding locations than an ordinary semiconductor chip. The circuit board [2] consists of a flexible substrate [21] which is made of an approximately 130 µm-thick polyimide resin tape, and of a conductive pattern [22] (lead) which is integrated onto this substrate [21]. The conductive pattern [22] is a conductive component, produced when the copper foil adhered to the substrate [21] is formed into a specified pattern on which gold plating of approximately 1 µm thickness has been applied. The area of the substrate [21] that corresponds to the position of the semiconductor chip [3] has been removed from the circuit board [2] to form a device hole [23] which is approximately quadrangular in outline. The semiconductor chip [3] is positioned on this device hole [23] and secured. This securing structure will be explained in more detail later. However, in this structure, the device hole [23] is filled with a molding agent [4] after the leads [221], which are part of the conductive pattern [22] and which protrude into the device hole [23] are bonded to the bumps [31] of the semiconductor chip [3], using the single-point bonding method, one location after another. The width of the leads [221] is narrower than that of other conductive patterns [22], making it easier to bond with the bumps [31]. Here, the bumps [31] were flattened when being bonded with the leads [221], and the leads [221] are bent slightly downward. In a semiconductor device [1] possessing the type of bonding structure in this example, the superimposing areas [211] of the circuit board [2] that overlap with the corners of the semiconductor chip [3] have been formed in the four corner regions; A, B, C, and D, of the device hole [23]. Also, dumzny bumps [32a] (spacers) have been formed in four locations in the active area [30] of the semiconductor chip [3], which overlaps the superimposing area [211]. These dummy bumps [32a] overlap the expanded width portion [20] of the conductive pattern [22]. This wider width ensures that dummy bumps [32a] will overlap the conductive pattern [22] even if the semiconductor chip [3] is slightly misaligned. However, because the dummy bumps [32a] are not electrically connected to any of the internal circuits of the semiconductor chip [3], they cannot cause a malfunction of the semiconductor device [1]. Although the dummy bumps [32a] overlap, they are not bonded to the conductive pattern [22] (the leads [221]). Consequently, the dummy bumps [32a] are not flattened and retain their initial thickness, unlike the bumps [31]. A superimposing area [212] of the circuit board [2] has also been formed inside the device hole [23], which overlaps the semiconductor chip [3]. The superimposing area [212] passes the approximate center of the device hole [23], and is connected to the approximate center of each of the four sides. Dummy bumps [32b] (spacers) have been formed in four locations in the active area [30] of the semiconductor chip [3], which overlaps the superimposing area [212]. These dummy bumps [32b] are not electrically connected to any of the internal circuits of the semiconductor chip [3]. Furthermore, because the dummy bumps [32b] are not bonded to the conductive pattern [22] (leads [221]), they are not flattened, thus retaining their initial thickness, unlike the bumps [31]. A high level of productivity can be achieved in the semiconductor device [1] configured in this way, because solder bumps are not used. Additionally, as shown in Figures 2 (a) and (b), a gap [t1] is automatically maintained between the circuit board [2] and the semiconductor chip [3] by the dummy bumps [32] ([32a and 32b]), of a thickness equivalent to that of the dummy bumps. This prevents the occurrence of short-circuiting between the conductive pattern [22] and the edge of the semiconductor chip [3]. Furthermore, because the thickness of the dummy bumps [32] is not affected by the process of bonding the leads [221] to the bumps [31], the dimension of the gap [t1] is determined by the initially-specified thickness of the dummy bumps [32]. Also, because the dummy bumps [32] overlap the conductive pattern [22], they reliably maintain the gap [t1] between the conductive pattern [22] and the semiconductor chip [3], thus ensuring the high reliability of the semiconductor device [1]. Furthermore, the dummy bumps [32] do not raise the cost of the semiconductor chip [3] because they can be formed simultaneously with the bonding bumps [31]. As schematically shown in Figure 3 (a), a longitudinal section before the bonding process, free dummy bumps [34 and 35] have been formed in the active area [30], which are not electrically required nor used for maintaining the gap [t1]. These free dummy bumps are in addition to the bumps [31] which are electrically required, and to the dummy bumps [32] which are necessary for maintaining the gap [t1]. The free dummy bump [34] is positioned inside the area where the device hole [23] has been formed. Although the free dummy bump [35] is positioned inside the area where the superimposing area [212] has been formed, it does not contact the circuit board [2] because no conductive pattern [22] has been formed there, as shown in Figure 3 (b), a longitudinal section after the bonding process. When free dummy bumps, such as [34] and [35], are formed, they can be used to secure a specified gap [t1] between the semiconductor chip [3] and the circuit board [2], for example, when the location of the superimposing areas [211 and 212] is changed on the circuit board [2]. Additionally, the semiconductor device [1] in this example possesses the following characteristics. Again, in Figure 1, the device hole [23] has been divided by the superimposing area [212] into four holes, [231], [232], [233], and [234]. In this case, the cross-over area [222] of the conductive pattern [22] only needs to transverse one of the holes, [232], even when it has been formed to transverse the entire device hole [23], and in addition, is reinforced by the superimposing area [212]. Likewise, the cross-over area [223] of the conductive pattern [22] transverses only the hole [232], and its tip is supported by the superimposing area [212]. Consequently, this cross-over area can be freely positioned in those areas that correspond to the active area [30] of the semiconductor chip [3], and the resulting conductive pattern will be very strong. Furthermore, because the circuit board [2] can be reinforced by retaining the superimposing areas [211 and 212] inside the device hole [23], the flexible circuit board [2] can be protected against unnecessary deformation. Furthermore, because the interior perimeter of the device hole [23] is formed into a complicated shape by the superimposing areas [211 and 212], the leads [221] can be made to protrude in either the longitudinal or the transverse direction. For example, the lead [221a] can be made to protrude along the interior perimeter of the device hole [23]. Consequently, leads that are positioned in orthogonal directions to each other [221a and 221b] can be formed even near the center of a side of the device hole [23], allowing for a high degree of wiring freedom. For these reasons, the semiconductor device [1] in this example is highly reliable, possesses a high degree of design freedom, and can be used in a wide range of applications. In addition, the superimposing area [212] has been formed to divide the device hole [23] by passing through the approximate center of the device hole [23]. Furthermore, a through-hole [230] has been formed in the area of the superimposing area [212] that corresponds to the center of the device hole [23], i.e., the approximate center of the semiconductor chip [3]. This structure offers the advantage of high productivity in assembly processing, as explained below. The process of assembling the semiconductor chip [3] to the circuit board [2] will be explained, with reference to Figures 3 (a) and (b). First, as shown in Figure 3 (a), the position of the semiconductor chip [3] relative to the device hole [23] of the circuit board [2] is determined. In this state, the superimposing area [211] overlaps the semiconductor chip [3]. From this state, the leads [221] and the bumps [31] are bonded, one location at a time, by applying ultrasonic vibration to the leads [221]. As a result, as shown in Figure 3 (b), the leads [221] are bent downward while the bumps [31] are flattened. In contrast, because the dummy bumps [32] are not bonded to the conductive pattern [22], they retain their initial thickness even after the bumps [31] and the leads [221] are bonded. Consequently, the gap [t1], which is equivalent to the initial thickness of the dummy bumps [32], is maintained between the circuit board [2] and the semiconductor chip [3]. Next, the molding agent [4] is injected into the device hole [23]. Here, the device hole [23] has been divided into four holes, 231, 232, etc., and the molding agent [4] is injected into each of these holes, 231, 232, etc. This allows the molding agent [4] to flow smoothly. Furthermore, the through-hole [230] has been formed in the section of the superimposing areas [211 and 212] that corresponds to the center of the device hole [23]. Air can escape through this through-hole [230] when the molding agent [4] is injected, allowing for the smooth flow of the molding agent [4], and thus, achieving high productivity in assembly processing. In this example, the dummy bumps [32] overlap the conductive pattern [22] that has been formed in the superimposing area [211] of the circuit board [2]. However, if the rigidity of the substrate [21] is relatively high, and if it is not necessary for the thickness of the conductive pattern [22] to contribute to the dimension of the gap [t1], a structure can be used in which the dummy bumps [32] directly overlap the substrate [21] itself in the superimposing area [211]. Working example 2 The basic structure of the semiconductor device in this example is the same as that of the semiconductor device related to Working example 1. For this reason, where the functions are the same, the same notations have been used and detailed explanations omitted. Figure 4 (a) is a longitudinal section that schematically shows the state of the semiconductor device in this example before the semiconductor chip is bonded to the circuit board, while Figure 4 (b) is a longitudinal section that schematically shows the state after the semiconductor chip is bonded to the circuit board. As in the semiconductor device related to Working example 1, in the semiconductor device [11] of this example shown in Figure 4 (a), a bump [31] (electrode for bonding), which is necessary for the electrical circuit, and a dummy bump [32] (spacer), which is not necessary for the electrical circuit, have been formed in the active area [30] of the semiconductor chip [3]. A device hole [23] has been formed on the side of the circuit board [2], and the lead [221] of the conductive pattern [22] protrudes into this hole. Furthermore, the circuit board [2] possesses a superimposing area [211] which overlaps the semiconductor chip [3] when this semiconductor chip [3] is correctly positioned against the device hole [23]. A conductive pattern [22] has also been formed in this superimposing area [211]. In this example, a protrusion [224] (spacer) that juts out from the conductive pattern [22], has been formed in the area of the conductive pattern [22] (which has been formed in the superimposing area [211]) that overlaps the dummy bump [32] when the semiconductor chip [3] is correctly positioned against the circuit board [2]. This protrusion [224] is a bump that has been transferred to the side of the circuit board [2]. Therefore, when the lead [221] and the bump [31] are bonded by applying ultrasonic vibration to the lead [221] in the single-point bonding method, the lead [221] is bent downward while the bump [31] is flattened, as shown in Figure 4 (b). In contrast, because the dummy bump [32] and the conductive pattern [22] (protrusion [224]) are not bonded, the dummy bump [32] retains its initial shape and thickness even after the lead [221] and the bump [31] are bonded. The protrusion [224] also retains its initial shape and thickness. A gap [t2], which is equivalent to the combined thicknesses of the dummy bump [32] and the protrusion [224], is maintained between the circuit board [2] and the semiconductor chip [3]. Consequently, no forming processing is required, and no short-circuiting occurs between the circuit board [2] and the edge of the semiconductor chip [3]. Furthermore, because the dimension of the gap [t2] is determined by the preset combined thicknesses of the dummy bump [32] and the protrusion [224], it need not be set too conservatively. Therefore, even a semiconductor device [11] which uses a bonding structure based on the single-point bonding method, can be made with thin profile and retain high reliability. Furthermore, the dummy bump [32] does not raise the cost of the semiconductor chip [3] because it can be formed simultaneously with the bumps for bonding [31]. since the planar structure of the semiconductor device [11] in this example is the same as that of the semiconductor device in Working example 1 shown in Figure 1, the molding agent [4] can be injected into each of the holes, 231, 232, etc. of the device hole [23]. Furthermore, air can escape through the through-hole [230] when the molding agent [4] is injected. Therefore, the injected molding agent [4] can flow smoothly. In this example, the protrusion [224] of the conductive pattern [22] overlaps the dummy bump [32] of the semiconductor chip [3]. However, if the protrusion [224] is sufficiently thick, it may overlap the active area [30] of the semiconductor chip [3], onto which an insulation coating has been applied. Working example 3 The basic structure of the semiconductor device in this example is the same as that of the semiconductor device related to working example 1. For this reason, where the functions are the same, the same notations have been used and detailed explanations omitted. Figure 5 (a) is a longitudinal section that schematically shows the state of the semiconductor device in this example before the semiconductor chip is bonded to the circuit board, while Figure 5 (b) is a longitudinal section that schematically shows the state after the semiconductor chip is bonded to the circuit board. In the semiconductor device [12] of this example in Figure 5 (a), a device hole [23] has been formed on the side of the circuit board [2], and a lead [221] of the conductive pattern [22] protrudes into this hole. This conductive pattern [22] consists of gold-plated leads. In this example, aluminum pads [38] have been formed on the semiconductor chip [3], and the lead [221] is bonded only to aluminum pad 38a (electrode for bonding). While aluminum pad 38a is necessary for the electrical circuit, aluminum pad 38b is not connected to any of the internal circuits of the semiconductor chip [3], and is not necessary for the electrical circuit. As can be seen in this example, this option is inexpensive, since no bumps are formed on the semiconductor chip [3]. The circuit board [2] possesses a superimposing area [211] which overlaps the semiconductor chip [3] when this semiconductor chip [3] is correctly positioned against the device hole [23]. The conductive pattern [22] has also been formed in this superimposing area [211]. The part of this conductive pattern [22] that overlaps the aluminum pad [38b] has been formed as a protrusion [225] (spacer) which juts out farther than other parts of the conductive pattern [22]. The protrusion [225] is formed by stopping the etching operation halfway in the area where the protrusion [225] is to be formed, when the conductive pattern [22] is being formed through etching. The part of the conductive pattern [22] that is positioned in the perimeter of the semiconductor chip [3] has been made thinner, and the protrusion [225] is thicker than this part. In the semiconductor device [12] thus configured, the lead [221] is bent downward when the lead [221] and aluminum pad 38a are bonded by applying ultrasonic vibration to the lead [221] in the single-point bonding method, as shown in Figure 5 (b). However, because the protrusion [225] is not bonded to the semiconductor chip [3], it is not flattened. Consequently, no short-circuiting occurs between the conductive pattern 22 and the edge of the semiconductor chip [3], since a gap [t3], which is equivalent to the initial thickness of the protrusion [225], is maintained between the circuit board [2] and the semiconductor chip [3]. Furthermore, because the thickness of the protrusion [225] does not change after the lead [221] is bonded to aluminum pad 38a, and the dimension of the gap [t3] is determined by the preset initial thickness of the protrusion [225], the gap [t3] need not be set too conservatively. Therefore, it is possible to achieve thin profile and high reliability in the semiconductor device [12] in this example. Additionally, because the protrusion [225] uses a part of the conductive pattern [22], it does not raise the cost of the circuit board [2]. Furthermore, the planar structure of the semiconductor device [12] in this example is the same as that of the semiconductor device in working example 1. Therefore, the molding agent [4] can be injected into each of the holes, 231, 232, etc. of the device hole [23]. Furthermore, air can escape through the through-hole [230] when the molding agent [4] is injected. Therefore, the injected molding agent [4] can flow smoothly. Although the protrusion [225] of the conductive pattern [22] overlaps the aluminum pad [38b] of the semiconductor chip [3] in this example, it may, for example, overlap the active area [30] of the semiconductor chip [3], onto which an insulation coating has been applied. Other working examples In addition to the above-mentioned working examples, if a superimposing area that overlaps the semiconductor chip is formed on a circuit board; and a spacer, whose thickness does not change after the conductive pattern and the bump are bonded, is formed on this superimposing area or on the surface of the semiconductor chip that overlaps the superimposing area; it would also be acceptable to use a protrusion of the substrate that comprises the circuit board itself, or an insulating protrusion that juts out from the active area of the semiconductor chip itself. Furthermore, it is possible to obtain effects similar to those obtainable with the single-point bonding method by using the gang-bonding method. When using the gang-bonding method, the bonding tool [T] should not have a flat bottom surface. Instead, as the structure of the bottom side of the bonding tool for gang bonding is schematically shown in Figure 6, the bonding tool [T] should have a concave area [T1] in order to avoid the superimposing areas [211 and 212] and the cross-over areas [222 and 223] of the conductive pattern. Potential industrial field of application As explained above, in the semiconductor device in this invention, a superimposing area which overlaps the semiconductor chip, which is positioned on a device hole, is formed on the circuit board side. A specified gap is maintained between this superimposing area and the semiconductor chip by a dummy bump formed on the semiconductor chip side, or by a spacer, such as a protrusion, formed on the conductive pattern of the superimposing area. Therefore, since this invention can maintain a specified gap between the superimposing area and the semiconductor chip, without the need for forming the lead of the circuit board even when a single-bonding method is used, it is possible to produce a thin profile semiconductor device, to prevent short-circuiting at the edge of the semiconductor chip, and to obtain high reliability. Furthermore, because the forming process can be omitted, a higher level of productivity can be achieved. Additionally, leads can be positioned in the region that corresponds to the active area of the semiconductor chip by forming conductive patterns in the superimposing area, thus enhancing both pattern design freedom and the general applicability of the semiconductor chip. When dummy bumps are formed on the semiconductor chip side, and protrusions of the conductive pattern are formed on the superimposing area of the circuit board, it is easy to form a wide gap between the circuit board and the semiconductor chip, equivalent to the combined thicknesses of the dummy bump formed on the semiconductor chip side and the protrusion. If superimposing areas are present in the four corner areas of the device hole, it is possible to obtain uniform gaps, even in a large-size semiconductor chip. Furthermore, if superimposing areas are also formed along the sides of the device hole, it is possible to obtain gaps of even greater uniformity, even for a larger-size semiconductor chip. The division of the device hole into multiple holes by the superimposing area allows the molding agent to flow smoothly, since it can be injected through each of the holes. Furthermore, even if a cross-over area traversing the divided hole is established in the conductive pattern, the cross-over area is reinforced by the superimposing area; thus improving circuit pattern design freedom while maintaining high reliability. The formation of a through-hole in the superimposing area that passes through the approximate center of the device hole, permits air to escape through the through-hole when a molding agent is injected; thus allowing the injected molding agent to flow smoothly.

Claims: A semiconductor device comprising: a circuit board (2) in which a conductive pattern (22) has been formed on an insulating substrate (21), a semiconductor chip (3) positioned over a device hole (23) of the said circuit board, the device comprising a plurality of spacers (32, 224, 225); wherein lead portions (221) of the conductive pattern protruding into the said device hole are bonded to bonding electrodes (31, 38) of the said semiconductor chip and the said circuit board possesses a superimposing area (211, 212) overlapping the said semiconductor chip, the superimposing area being formed by superimposing one upon the other a part of said insulating substrate and the conductive pattern, the conductive pattern being arranged on the said part of said insulating substrate such that it faces toward the semiconductor chip, and characterised in that the said plurality of spacers (32, 224, 225) is provided on a surface of the said superimposing area and not bonded with the said semiconductor chip and/or is provided on a surface of the area of the said semiconductor chip overlapping said superimposing area and not bonded with the said superimposing area, at least one portion of the conductive pattern being arranged on a region of the substrate existing between a spacer and an adjacent spacer, such that the said spacers are positioned outside the device hole between the said circuit board and the said semiconductor chip to maintain a specified gap (t1, t2, t3) between the two. The semiconductor device of claim 1, further characterised in that the said spacer is a dummy bump (32) that is not bonded to the said conductive pattern on the surface of the said semiconductor chip which overlaps the said superimposing area, and is positioned between the said circuit board and the said semiconductor chip to maintain a specified distance between the two. The semiconductor device of claim 2, further characterised in that the said conductive pattern overlaps the said dummy bump in the said superimposing area. The semiconductor device of claim 1, further characterised in that the said spacer is a protrusion (224, 225) of the said conductive pattern, that is not bonded to the said bonding electrode on the side of the said superimposing area, and is positioned between the said circuit board and the said semiconductor chip to maintain a specified distance between the two. The semiconductor device of claim 4, further characterised in that the said semiconductor chip possesses both bumps (31) that are used as the said bonding electrodes, and dummy bumps (32) which are not bonded to the said protrusion, in those locations overlapping the said protrusion. The semiconductor device of claim 4, further characterised in that the said semiconductor chip possesses both pads (38a) that are used as the said bonding electrodes, and dummy pads (38b) which are not bonded to the said protrusion, in those locations overlapping the said protrusion. The semiconductor device of any preceding claim, further characterised in that the said device hole is approximately quadrangular in outline, and the said superimposing area (211) exists in the four comer areas of the said quadrangle. The semiconductor device of claim 7, further characterised in that the said superimposing area also exists along each side of the said device hole. The semiconductor device of any preceding claim, further characterised in that the said superimposing area (212) is formed inside the said device hole, thus dividing the said device hole into multiple holes. The semiconductor device of claim 9, further characterised in that the said superimposing area passes through the approximate centre of the said device hole, dividing the said device hole into multiple holes; and in that a through-hole (230) has been formed in the area of the said superimposing area that corresponds to the approximate centre of the said device hole. The semiconductor device of either claim 9 or 10, further characterised in that the said conductive pattern possesses a cross-over area that traverses at least one of said multiple holes. A method of producing a semiconductor device comprising: a circuit board (2) in which a conductive pattern (22) has been formed on an insulating substrate (2), and a semiconductor chip is positioned over a device hole (23) of the said circuit board and the said circuit board possesses a superimposing area (211, 212) overlapping the said semiconductor chip, the superimposing area being formed by superimposing one upon the other a part of said insulating substrate and the conductive pattern, the conductive pattern being arranged on the said part of said insulating substrate such that it faces toward the semiconductor chip; characterised by : forming a plurality of spacers on a surface of the said superimposing area and/or on a surface of the area of the said semiconductor chip overlapping said superimposing area, at least one portion of the conductive pattern being arranged on a region of the substrate existing between a spacer and an adjacent spacer, positioning the semiconductor chip over the device hole and bonding a lead portion (221) of the conductive pattern protruding into the said device hole to a bonding electrode of the said semiconductor chip the spacers formed on the surface of the superimposing area being not bonded with the semiconductor chip and/or the spacers formed on the surface of the semiconductor chip being not bonded with the superimposing area, such that the said spacers are positioned outside the device hole between the said circuit board and the said semiconductor chip to maintain a specified gap (t1, t2, t3) between the two. The method of claim 12, characterised in that the thickness of the spacer does not change before or after the said lead and the said boundary electrodes are bonded to maintain the said specified gap (t1, t2, t3) between the said circuit board and the said semiconductor chip.

Inventors: IIJIMA YOSHITAKA, SEKI SHIGEAKI, IIJIMA, YOSHITAKA, SEKI, SHIGEAKI, IIJIMA, YOSHITAKA SEIKO EPSON CORPORATION, SEKI, SHIGEAKI SEIKO EPSON CORPORATION
Applicants: SEIKO EPSON CORP, SEIKO EPSON CORPORATION
Application year: 1994
Main classification: H01L21
IPC codes: H01L21, H01L23